Process for manufacturing recorder pens or the like



May 2, 1967 F. KUYT 3,31%,631

PROCESS FOR MANUFACTURING RECORDER PENS OR THE LIKE Filed Dec. 7, 1964 FIG. 3 FIG. 4

MOTOR FRETS KUYT INVENTOR AT RNE 8 United States Patent York Filed Dec. 7, 1964, Ser. No. 416,476 3 Claims. (Cl. 29-558) This invention relates to a novel process for manufacturing recorder pens and more particularly to a novel process for rounding off and polishing pen points of the type used in strip chart recorders.

Strip chart recorders have come into widespread use in conjunction with electrical test equipment. Recorders of this type are responsive to frequent changes indicated by the electrical equipment. These changes are often rapid and require a pen to move a relatively long distance in a relatively short interval of time. At other times the pen is moved over a comparatively lesser distance during a similar time interval. Frequently a pen is temporarily withdrawn from use which may cause the ink to dry in the point. Such hardening impedes the flow of ink when the pen is returned to service. One approach which has been relatively successful in solving the aforementioned problems is disclosed in my copending application entitled Recorder Pen, Ser. No. 352,597, filed Mar. 17, 1964, and assigned to the same assignee as the present application.

In manufacturing pens for strip chart recorders it has been found that a rounded polished tip on the point is effective for producing a finer line. Additionally, there is a substantial reduction in the amount of clogging caused by hardening of the ink. Furthermore pens having a rounded polished tip write without scratching, cause less friction and generally have greatly improved characteristics.

Because of the relatively small size of the points for use in recorder pens, there is a problem associated with rounding these points to the preferred configuration. Advantageously, the novel process disclosed herein facilitates rounding off the points of a recorder pen. The process not only produces an improved pen but also may be accomplished relatively inexpensively, so that, the pens offer an added advantage in the competitive commercial market.

Briefly, the method according to the present invention comprises providing a flexible abrasive wheel which is rotatable about a first axis and rotating the abrasive wheel about a second axis. The writing tube of the pen is chamfered and subsequently held against the abrasive wheel until a rounded ofl configuration is obtained. The flexible wheel flexes and forms itself to a rounded shape to thereby round off the edge of the writing tube. Progressive stages of coarse and fine grinding, as well as a bufling step are provided in order to obtain the desired finish on a writing tube.

The invention will now be described in more detail in connection with the accompanying drawings; in which,

FIG. 1 is a perspective view illustrating a writing tube of the type provided in a recorder pen;

FIG. 2 is a perspective view illustrating a writing tube of the type shown in FIG. 1 wherein the pen point has been polished in accordance with the present invention;

FIG. 3 is a cross sectional view illustrating a writing tube which has been chamfered in accordance with a first step of the novel method disclosed herein;

FIG. 4 is a cross sectional view illustrating a writing tube pressed against a flexible wheel as it appears during the second, third and fourth stages of the method disclosed herein, and

FIG. 5 is a perspective view illustrating the apparatus for carrying out the grinding and polishing steps in accordance with the present invention.

The writing tube illustrated in FIGS. 1 and 2 comprises a stainless steel tube 10 having an outside diameter of about .016 inch and a wall thickness of about .004. The tube 10 is disposed in a suitable body 12. In order to produce a pen with optimum characteristics it is desirable to round ofl and polish the tube 10 to produce the shape shown in FIG. 2. Pens having a polished surface have less drag, produce a finer line and have less tendency to clog.

It is also desirable to manufacture recorder pens with improved characteristics without incurring a substantial increase in the costs thereof. For example, the relatively small sizes of the pens would require precision tolerances for machining the desired configuration. It has now been found that the desired configuration may be produced in accordance with the novel method disclosed herein at a minimal expense by a relatively unskilled operator.

The method according to the present invention includes four stages which comprise chamfering, coarse grinding, fine grinding and polishing operations.

The chamfering illustrated in FIG. 3 is accomplished by drilling the interior portion 13 of the writing tube'10 with a drill such as a drill. The pens normally have approximately .013" outside diameter and a .008" inside diameter. In order to produce optimal results about /3 of the wall thickness or about .001 on the inside diameter is beveled or chamfered by drilling at a rate of approximately 2450 revolutions per minute and slowly advancing the drill for a distance of about 0.001" into the writing tube.

A flexible rubber disk 16 shown in FIG. 4 having a diameter of about 1" and a coarse grit is rotated about an axis at about 3100 revolutions per minute. The rotating disk itself is rotatable about a second axis to provide a convenient method of finding a fresh spot on the abrasive surface for the grinding of each successive pen tube. Additionally, the rotation of the rotatable disk provides a rotation about the axis of the pen tube during the polishing operations.

The disk used in the first step of the grinding operation has a relatively coarse grit dispersed in a relatively flexible rubber material. For example, the disks used in this stage of the operation are commercially available as a Norton AlSOBZRR (Grit) 873762 (7). The chamfered writing tube is forced against the rotating disk to obtain an initial rough shape on the point. As shown in FIG. 4, the disk 16 conforms to the desired shape due to its flexibility to thereby produce a rounded surface on the end of the chamfered tube 10.

A medium grit disk such as a Norton A220B8RR (Grit) 873763 (7) is provided and rotated in a similar manner to the aforementioned coarse disk. The writing tube is forced against the medium disk during the third stage of the operation, while the disk is eccentrically rotated about the axis at approximately 3100 revolutions per minute.

The writing tube is forced against a polishing disk in order to obtain a final polish. The polishing disk has a very fine abrasive such as a fine powder dispersed in a rubber material and is eccentrically rotated in the same manner and at about the same speed as the coarse and medium disks. An example of the polishing disk is a Norton A280B2RR (Grit) 873764 (7).

The apparatus shown in FIG. 5 illustrates the eccentric rotation of the various disks. For example the shaft 50 is coupled to suitable driving means such as the motor 52 to thereby rotate the shaft 50 in a counterclockwise direction at approximately 3100 revolutions per minute. A second shaft 56 is freely rotatable about its own axis and will rotate in response to the rotation of the shaft 50. Accordingly, a disk 60 which is fixed to the second shaft 56 is rotated about two axes simultaneously in the same direction to thereby produce an eccentric motion. The pen is held in a manner so that the writing tube is forced against the rotating disk 60 during each of the grinding and polishing stages. Accordingly the disk 60 grinds the writing tube to the configuration shown in FIGS. 2 and 4.

While the invention has been described in connection with a preferred embodiment it should be understood that it may be modified or embodied in other forms without departing from the scope of the dependent claims.

' What is claimed is:

1. A method for polishing writing tubes of the type used in strip chart recorders comprising the steps of chamfering an inside surface of the writing tube at one end thereof, providing a rotatable flexible abrasive disk of coarse grit which is rotatable about a first axis and rotating the disk simultaneously about a second axis to thereby produce an eccentric rotational movement, forcing the chamfered end of the tube against the eccentrically rotating disk to thereby round off the end surface thereof, providing a rotatable flexible abrasive disk of medium grit which is rotatable about a first axis and rotating the disk simultaneously about a second axis to thereby produce an eccentric rotational movement, forcing the rounded end of the writing tube against the eccentrically rotating medium grit disk to thereby produce a finer finish on the writing tube, and providing a rotatable flexible abrasive disk of fine grit which is rotatable about a first axis and rotating the disk about a second axis to thereby produce an eccentric rotational movement, forcing the rounded end of the writing tube agianst the eccentrically rotating fine grit disk to thereby produce a final polish on the end surface thereof.

2. A method for polishing writing tubes according to claim 1 in which the disks are rotated in a counterclockwise direction at about 3100 revolutions per minute.

3. A method for polishing writing tubes or the like comprising the step of removing a beveled portion of about .001 from an inner surface of the writing tube by drilling to a depth of about .001", providing a rotatable flexible abrasive disk of coarse grit which is freely rotatableabout a first axis and rotating the disk about a second axis to thereby produce an eccentric rotational movement, forcing the chamfered end of the tube against the eccentrically rotating medium grit disk to thereby proend surface thereof, providing a rotatable flexible abrasive disk of medium grit which is freely rotatable about a first axis and rotating the disk simultaneously about a second axis to thereby produce an eccentric rotational movement, forcing the rounded end of the writing tube against the eccentrically rotating medium grit disk to thereby produce a finer finish on the writing tube, and providing a rotatable flexible abrasive disk of fine grit which is freely rotatable about a first axis and rotating the disk about the second axis to thereby produce an eccentric rotational movement, forcing the rounded end of the writing tube against the eccentrically rotating fine grit disk to thereby produce a final polish on the end surface thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,589,239 6/1926 Scott.

2,115,461 4/ 1938 Hartmann.

2,170,811 8/1939 Cornell 29-558 X 2,824,319 2/1958 Nagere 29-557 X 3,181,228 4/1965 Drovbay 29--558 X FOREIGN PATENTS 138,155 9/1960 Russia.

JOHN F. CAMPBELL, Primary Examiner.

P. M. COHEN, Assistant Examiner. 

1. A METHOD FOR POLISHING WRITING TUBES OF THE TYPE USED IN STRIP CHART RECORDERS COMPRISING THE STEPS OF CHAMFERING AN INSIDE SURFACE OF THE WRITING TUBE AT ONE END THEREOF, PROVIDING A ROTATABLE FLEXIBLE ABRASIVE DISK OF COARSE GRIT WHICH IS ROTATABLE ABOUT A FIRST AXIS AND ROTATING THE DISK SIMULTANEOUSLY ABOUT A SECOND AXIS TO THEREBY PRODUCE AN ECCENTRIC ROTATIONAL MOVEMENT, FORCING THE CHAMFERED END OF THE TUBE AGAINST THE ECCENTRICALLY ROTATING DISK TO THEREBY ROUND OFF THE END SURFACE THEREOF, PROVIDING A ROTATABLE FLEXIBLE ABRASIVE DISK OF MEDIUM GRIT WHICH IS ROTATABLE ABOUT A FIRST AXIS AND ROTATING THE DISK SIMULTANEOUSLY ABOUT A SECOND AXIS TO THEREBY PRODUCE AN ECCENTRIC ROTATIONAL MOVEMENT, FORCING THE ROUNDED END OF THE WRITING TUBE AGAINST THE ECCENTRICALLY ROTATING MEDIUM GRIT DISK TO THEREBY PRODUCE A FINER FINISH ON THE WRITING TUBE, AND PROVIDING A ROTATABLE FLEXIBLE ABRASIVE DISK OF FINE GRIT WHICH IS ROTATABLE ABOUT A FIRST AXIS AND ROTATING THE DISK ABOUT A SECOND AXIS TO THEREBY PRODUCE AN ECCENTRIC ROTATIONAL MOVEMENT, FORCING THE ROUNDED END OF THE WRITING TUBE AGAINST THE ECCENTRICALLY ROTATING FINE GRIT DISK TO THEREBY PRODUCE A FINAL POLISH ON THE END SURFACE THEREOF. 